the hose that is connected to the front diff. and travels up with a white end plug is used for what? I was thinking just a blow off or vent, mine rubbed on the drive shaft wondering how important it is.

 

That would be the differential breather tube. I believe the white device on the end is a check valve intended to keep debris from entering and clogging the tube. A clogged tube could cause the seals to fail and leak prematurely.